Spirally wound pin connector



y 9, 1967 D. PHILLIPS 3,319,217

SPIRALLY WOUND PIN CONNECTOR Filed Feb. 25, 1966 4 Sheets-Sheet 1 ya amm xrraeA/a r May 9, 1967. 0.1.; PHILLIPS 3,319,217

SPIRALLY WOUND PIN CONNECTOR 4 Sheets-Sheet 2' Filed Feb. 25, l966 zMTM/ M y W I l May 9, 1967 D. L. PHILLIPS 1 SPIRALLY WOUND PIN CONNECTOR Filed Feb. 25, 1966 1 4Sheets-Sheet 1/0 I 0 01i 0 0 (ii \i! P 1 0ca oooxanoraoo .154 1,2

United States Patent Ofiice 3,319,2l7 Fatentecl May 9, 15967 3,319,217 SPIRALLY WOUND PIN CONNECTOR Delbert L. Phillips, Malibu, Califi, assignor to New Twist Connector Corporation, Santa Monica, Calif., a corporation of California Filed Feb. 25, 1966, Ser. No. 530,142 8 Claims. (Cl. 339176) This application is a continuation-in-part of my copending application Ser. No. 418,381, filed Dec. 7, 1964, now Patent No. 3,255,430, entitled, Spirally Wound Pin Connector which, in turn, is a continuation-in-part of my abandoned application Ser. No. 117,881, filed June 19, 1961, of the same title, which, in turn, is a continuationin-part of my abandoned application Ser. No. 808,783, filed Apr. 24, 1959 and entitled, Plug Connector.

The invention relates to releasable connectors for electric circuits, and more particularly, relates to a pin connector and a cooperating socket connector into which the pin connector fits in a retractable manner.

The invention meets the need for a pin connector that is highly efficient and reliable over a long service life and at the same time is of simple, inexpensive construction suitable for mass production. The pin connector of the present invention may be produced entirely by automatic machinery at a total labor and material cost that is exceedingly low.

The invention also meets the need for a pin connector that is resiliently contractible in cross-sectional dimension. Such a pin connector is highly advantageous for a number of reasons.

In the first place, a resiliently contractible pin connector may be oversized relative to the cooperating socket so that the pin connector is forcibly contracted by the socket to assure adequate frictional engagement with the socket. In the second place, such a construction permits a liberal range of tolerances in the dimensioning of a pin connector to fit into a socket of a given size and, conversely permits tolerances in the dimensioning of the socket. In the third place, a pin connector that is resiliently contracted by the cooperating socket has high resistance to vibration. In the fourth place an extensive portion of the pin connector makes pressure contact with the cooperating socket to minimize contact resistance at the connection.

Broadly described, the pin connector comprises a longitudinal axial core with a cluster of resiliently flexible wires surrounding the core, the cluster being oversized in cross-sectional dimension relative to the cooperating socket connector. The opposite ends of the wires of the cluster are fixedly connected to the core and the intermediate portions of the wires of the cluster are spaced radially outward from the core to permit resilient radial contraction of the cluster by a cooperating connector socket.

In some practices of the invention a second outer set of wires is added to the cluster to give the pin a relatively large diameter. The second set surrounds an inner set of wires and is anchored in the same manner to the Opposite ends of the axial core. Preferably the two sets of wires of the cluster are helical wires and the two sets are wound in opposite directions.

A feature of the invention is that the pin connector in its simplest form comprises a single pin element with both of its ends adapted for insertion into two corresponding sockets. As will be explained, such a pin element may be used for circuit connections in the general manner of a dowel without the necessity of applying solder. A plurality of such double ended pin elements may be used to electrically interconnect two printed circuit panels with the panels positioned face to face.

A further feature of primary importance is the concept,

of making a pin element that is resiliently contractible in diameter but nevertheless has extensive surfaces of the same radius as the inside radius of the socket in which the p1n element is to be used. Thus although the pin connectoncomprises essentially a cluster of relatively small wires in cooperation with an axial core, at least some of the small Wires that provide the outer circumferential surface of the pin connector have curved surfaces that match the inside radius of the socket to make more than line contact with the inner circumferential surface of the socket.

The features and advantages of the invention may be understood from the following description and the accompanying drawings.

In the drawings, which are to be regarded as merely illustrative:

FIG. 1 is a view of a pin connector embodying the invention, the view being partly in side elevation and partly in section;

FIG. 2 is a cross-sectional view on an enlarged scale showing one construction that may be employed for the pin element of FIG. 1;

FIG. 3 is a similar cross-sectional view showing another construction that may be employed for the pin element of FIG. 1;

FIG. 4 is a similar cross-sectional view showing another construction that may be employed for the pin element of FIG. 1;

FIG. 5 is a similar cross-sectional view showing still another construction that may be employed for the pin element of FIG. 1;

FIG. 6 is a similar cross-sectional view showing another construction that may be employed for the pin element shown in FIG. 1;

FIG. 7 is a diagrammatic section view of a reciprocative tool that may be employed to cut away material of the outer wires of a pin element to increase the area of contact of the pin element with a socket of a given inside diameter;

FIG. 8 is a similar view of a reciprocative tool which may be employed to burnish the outer wires of a pin element for the same purpose;

FIG. 9 is a side elevation of the pin connector of the in- Vention in its simplest form comprising solely a pin element, the opposite ends of which may be inserted into cooperative socket connectors;

FIG. 10 is a sectional view showing how the pin element of FIG. 9 may be employed to electrically connect two printed circuit boards with the two boards in faceto-face relationship;

FIG. 11 is a side elevational View, partially broken away, of a pin connector that consists solely of the pin element with two sets of helical wires;

FIG. 12 is a cross-sectional view of the pin element shown in FIG. 11;

FIG. 13 is a sectional View showing how the pin element of FIG- 11 may be employed to electrically connect two printed circuit boards with the two boards in faceto-face relationship;

FIG. 14 is a cross section along the line A-A of FIG. 10 showing how a pin element of the cross section shown in FIG. 2 cooperates with a surrounding socket;

FIG. 15 is a similar view showing how a pin element of the cross section shown in FIG. 3 cooperates with a surrounding socket;

FIG. 16 is a similar view showing how a pin element of the cross section shown in FIG. 4 cooperates with a surrounding socket;

FIG. 17 is a similar view showing how a pin element of the cross section shown in FIG. 5 cooperates with a surrounding socket;

FIG. 18 is a similar view showing how a pin element of the cross section shown in FIG. 6 cooperates with a surrounding socket;

FIG. 19 is a cross section along the line BB of FIG. 13 showing how a pin element of the cross section shown in FIG. 12 cooperates with a surrounding socket;

FIG. 20 is a diagram showing how an outer wire makes surface-to-surface contact with the inner circumferential wall of the socket if the radius of curvature of the surface of the outer wire is the same as the inside radius of the socket;

FIG. 21 is a similar diagram showing how an outer wire of a cluster of wires of a pin element makes only line contact with a surrounding socket if the surface of the outer wire has a radius of curvature less than the inside radius of the socket;

FIG. 22 is a similar diagram showing how the outer wire of a pin element makes contact with the surrounding socket along two lines if the radius of curvature of the outer surface of the wire is greater than the inside radius of the socket;

FIG. 23 is a side elevation partly in section of a double ended pin connector, the two pin elements of which are identical with the pin element shown in FIG. 9;

FIG. 24 is a side elevation partly in section of a double ended connector, the two pin elements of which are identical with the pin elements shown in FIG. 11;

FIG. 25 is a side elevational view of a pin element with a shank member welded thereto, the shank member comprising a short length of solid wire;

FIG. 26 is a face view of a multiple socket connector that may be employed to interconnect multiple conductors such as the multiple wires of two matching cables;

FIG. 27 is a side elevational view of the connector shown in FIG. 26 with parts broken away;

FIG. 28 is a side elevational view of a multiple pin connector that may be employed with the multiple socket connector shown in FIGS. 26 and 27, a portion of the structure being broken away;

FIG. 29 is a face view of the multiple pin connector shown in FIG. 28;

FIG. 30 is a side elevational view showing the multiple pin connector of FIGS. 28 and 29 mated with the multiple socket connector of FIGS. 26 and 27, a portion of the structure being broken away;

FIG. 31 is an enlarged detail of FIG. 30 showing a pin element surrounded by a socket element;

FIG. 32 is a cross-sectional view illustrating a stage in the fabrication of an orifice die that may be employed in one practice of the invention;

FIG. 33 is a similar view of the finished orifice die;

FIG. 34 is a view showing the cross-sectional configuration of a multiple wire strand before it is processed by the die shown in FIG. 33;

FIG. 35 is a view similar to FIG. 34 showing the reduced diameter and cross-sectional configuration of the multiple wire strand when it is confined by the orifice die of FIG. 33; and

FIG. 36 is a similar cross-sectional view after a short length of the strand has been processed to form a pin connector element and after the pin connector element has been expanded to a diameter that is greater than the diameter of the socket in which the pin element is to be inserted.

The first embodiment of the invention illustrated by FIG. 1 includes a base member in the form of a ferrule 40, the bore of which is of stepped configuration to receive the end of an insulated wire 42. The wire 42 is shownanchored in the bore by solder 44 with the insulation 45 of the wire extending into the enlarged end of the bore. If desired, the ferrule 40 may be crimped to engage the wire 42 with the solder omitted. The cross section along the line C-C of'the pin element 43 of the pin connector may be any of the cross sections shown in FIGS. 26. Thus as shown in FIG. 2, the pin element 43- of the pin connector may comprise an axial core wire 46 and a cluster of helically formed wires 48 surrounding the core wire.

It is contemplated that the two ends of the helical wires 48 of the cluster will be fixedly connected with the corresponding ends of the core wire 46. In this particular embodiment of the invention, the ferrule 40 is crimped inward as indicated at 5'0 to grip the cluster of wires 48 and the inner ends of the cluster wires 48 and the core wires 46 are fused together by an arc welding technique to form a solid metal inner end 52. In the same manner the outer ends of the helical wires 48 and the core wire 36 are fused together by an electric arc to produce a similar solid outer end 54, the outer end having a smooth rounded nose as shown.

It is contemplated that the core wire 46 will be made of highly conductive material and soft copper is presently preferred for this purpose. On the other hand, it is contemplated that the helical wires 48 will be of resilient or spring-like construction. For this purpose the helical wires 48 may be made of beryllium copper that is threefourths hard.

As clearly indicated in FIG. 2, the helical wires 43 at their intermediate portions are spaced substantially radially outward from the core wire 46 to permit the pin element of the connector to be yieldingly contracted radially by the cooperating socket connector in which it is inserted. It may be further noted in FIG. 2 that the core wire 46 has shallow recesses or indentations 55 on its peripheral surface corresponding to the helical wires 48 to provide additional clearance for radial inward flexure of the helical wires.

The unrestrained cross-sectional dimension of the clus-' ter of helical wires 48 in FIG. 2, i.e. the overall crosssectional dimension of the pin element of the pin connector before the pin element is inserted into a cooperating socket connector, is greater than the internal cross-sectional dimension or inside diameter of the cooperating socket. Consequently, insertion of the pin element into the cooperating socket connector causes the pin element to be radially contracted, the major portions of the helical wires 48 being flexed towards the core wire 46. On the other hand, the completely contracted cross-sectional dimension of the pin, i.e. the cross section when the cluster wires 48 are forced inward to seat solidly in the indentations 55, is preferably too small for effective fit in the cooperating socket connector.

The construction may be understood by considering the preferred method of fabrication. First, the outer wires 48 are wound helically tight around the core wire 46 to make a strand of wires and then the strand of wires is drawn through a die orifice that contracts the strand with consequent forcing of the relatively hard beryllium copper helical wires into the relatively soft copper core wire with resulting formation of the helical indentations 42 in the core wire.

After the strand of wire has been processed in this manner, the end of the strand is fused by an electric arc and is inserted into the ferrule 40 and the ferrule 40 is crimped as indicated at 50 in FIG. 1. The wire strand is then cut to the desired length for a pin element and the outer ends of the wires of the severed strand are then bonded together .by an electric arc of sufficient intensity and duration to cause the metal at the ends of the wire-v to melt and form the single rounded outer end or nose 54..

At this point in the procedure of fabricating the pin connector, the helically formed wires 48 are seated snugly in the helical indentations of the core wire 46. The next step is to shorten the core wire 46 to cause the helically formed wires 48 to be flexed or biased outward in the manner shown in FIG. 2.

The preferred procedure for shortening the core wire 46- is simply to subject the pin element to a suitable endwise impact. An alternate procedure which is also satisfactory is simply to grip the two ends of the pin element and twist the pin element in an unwinding direction for a few degrees. The unwinding operation in itself causes the helical wires 48 to bulge radially outward from the core wire 46 and the shortening of the core that is caused by the twisting of the core wire further expands the cluster of helically formed wires.

In a pin element fabricated as described up to this point, all of the outer wires that form the outer circumferential surface of the pin element are of circular configuration and therefore make only line contact with the circular socket in which the pin element is inserted. In the preferred practice of the invention, however, portions of the surfaces of the outer wires of a pin element have radii of curvature that are substantially equal to the radius of the socket in which the pin element is to be inserted, the consequence being that each of the outer wires of the pin element makes more than line contact with the inner surface of the socket. Such a pin element has a relatively large area of contact with the socket for reduced electrical resistance. A further advantage is that the unit pressure between the pin element and the surrounding socket is reduced with consequent reduction in wear when the pin element is repeatedly withdrawn and reinserted in the socket.

I have found that the desired change in cross-sectional configuration of the outer wires of a pin element may be achieved either by removing metal from the outer wires or by burnishing the outer wires in a manner that changes the cross-sectional configuration without removing metal. In one practice of the invention an annular tool is used that has an inner circumferential abrasive surface of an inside diameter that is equal to the insidediameter of the socket in which the pin element is to be inserted. Such a tool may have one or more inner circumferential cutting edges or may have an inner surface made of hard abrasive particles. When an expanded pin element is inserted into such a tool the pin element is contracted with consequent creation of radial pressure between the pin element and the tool. The tool is then reciprocated relative to the pin element, preferably at a vibratory rate, to produce the desired cross-sectional configuration of the outer wires of the pin element.

FIG. 7 shows diagrammatically a tool that may be used to remove material from the wires in the manner described. The tool comprises a suitable holder 56 in which is mounted a ring-shaped cutting tool 58 that is made of exceedingly hard material and has an inner circumferential cutting edge of the desired predetermined diameter. Suitable means (not shown) is employed to reciprocate or fabricate the holder 56 as indicated by the double headed arrow. The pin element up to this point has been fabricated by fusing the cluster wires to the core at each of the two opposite ends of the pin element and the pin element has been expanded radially as heretofore described to an outside diameter that substantially exceeds the diameter of the socket into which the pin element is to be inserted.

The inside diameter of the ring-shaped tool'58 is the same as the inside diameter of the socket with which the pin element is to be used so that the removal of the material of the cluster wires of the pin element by the ringshaped tool results in the individual helical wires 48 being locally noncircular in configuration as may be seen in FIG. 2, each cluster wire 48 having a cylindrically curved portion 48a where the radius of curvature is the radius of the inner circumferential surface of the socket into which the pin element is to be inserted.

IN FIG. 2 where the pin element is free from restraint the outside diameter of the pin element indicated by the outer dotted line circle is substantially greater than the diameter of the complementary socket. The innermost of the three dotted circles is the solid diameter of the pin element, i.e. the diameter of the pin element when the cluster wires 48 are seated firmly in the indentations 55 of the core wire 45. The intermediate dotted circle 6 represents the inside diameter of the complementary socket. When the pin element is inserted into the complementary socket it is sufiiciently compressed to insure highly effective contact between the pin element and the socket. It is apparent that the pin element may be fabricated with liberal tolerance, it being essential merely that the pin have an unrestrained diameter greater than the inside diameter of a complementary socket and that the so-called solid diameter of the pin element be less than the inside diameter of the complementary socket.

FIG. 8 shows a holder 56a which carries a ring-shaped tool 5'8 which is a burnishing tool having the function of changing the shape of the outer cluster wires 48 primarily by deforming the wires rather than primarily by removing material from the wires.

FIG. 3 shows in cross-sectional configuration a pin element corresponding to the pin element shown in FIG. 2 wherein the burnishing tool of FIG. 8 has been employed instead of the cutting tool of FIG. 6. The cluster wires 59 in FIG. 3 which are connected at their ends to a core wire 60 are somewhat oval in cross-sectional configuration with outer surfaces 59a of the cluster wires having radii of curvature corresponding to the inside radius of the complementary socket. Here again an outermost dotted circle represents the outside diameter of the pin element in its unrestrained state, the innermost dotted circle represents the solid diameter of the pin element and the intermediate circle is the inside diameter of the complementary socket.

FIG. 20 shows diagrammatically how a wire 61 of a cluster mates with the inner circumferential surface 62 of a complementary socket when the outer surface 61a of the cluster wire has a radius of curvature that is equal to the inside radius of the socket. It is apparent that the cluster wire 61 makes surface-to-surface contact with the socket as distinguished from line contact.

FIG. 21 indicates the result of the outer surface 63a of a cluster wire 63 having a smaller radius of curvature than the inside radius of the inner circumferential sur face 62 of the socket. It is apparent that the cluster wire 63 in FIG. 21 makes contact with the socket along a single longitudinal line.

FIG. 22 indicates the result of making the surface 64a of a cluster wire 64 with a greater radius of curvature than the radius of curvature of the socket wall 62. It is apparent that the cluster wire 64 in FIG. 22 makes contact with the socket along two longitudinal lines.

It is apparent the use of a relatively soft copper for the core wire is advantageous for -a number of reasons. 111 the first place the soft copper offers relatively low resistance to the flow of current to minimize the contact resistance at an electrical joint that is completed by the pin connector. In the second :place the relatively soft copper is readily deformed to provide the indentations for greater freedom of radial movement of the outer helically formed wires.

On the other hand, the use of beryllium copper for the outer helically formed wires is advantageous because the beryllium copper is hard enough to form the indentations in the core wire. A further advantage is that the resiliency of beryllium copper makes the helically formed wire function as springs so that the helical wires make effective contact with a surrounding socket and resilient- 1y conform to the dimensions and configuration of the socket. Each of the helical springs makes contact with -a surrounding socket throughout the major portion of the length of the spring and since there is a plurality of the helically formed wires, say four, six, eight of more wires, the connector pin and the socket in which the connector pin is inserted have an extensive area of mutual contact. The extensive area of mutual contact not only lowers the resistance at the electrical connection but also results in longevity for the connector pin.

FIG. 4 shows in cross section how a pin element may have an axial core wire 65 in combination with a cluster of six helical wires 66, the six helical wires being smaller in diameter than the four helical wires 4-8 of FIG. 2. As shown in FIG. 4, the core wire 65 has peripheral recesses or helical indentations 68 corresponding to the individual helical wires 66 and the cluster of wires 66 have been abraded to give them outer surfaces 66a of a radius of curvature corresponding to the radius of the complementary socket.

FIG. 6 shows how a plurality of three wires may be used for a core of a pin element instead of a single wire. The three wires 72 of the core are twisted together and are surrounded by a cluster of helical wires 73, the direction of twist of the three core wires being opposite to the helical direction of the outer wires 73. The six wires 73 of the cluster have each been processed by the cutting tool 8 shown in FIG. 7 with the consequence that each cluster wire has an outer circumfereni-al surface 7311 that conforms to the curvature of a complementary socket wall.

FIG. 9 shows how the invention may be embodied in a pin connector, both ends of which may be inserted into corresponding sockets. The pin connector shown in FIG. 8 is the simplest form of the invention and consists solely of the pin element 43 of previously described FIG. 1. A suitable metal core (not shown) extends from one welded end of the pin element 43 to the other welded end and a cluster of helical wires surrounds the core throughout its length, the opposite ends of the helical formed wires being welded to the opposite ends of the core wire as indicated at 52 and 54. The cross section of the pin element 4 3 in FIG. 9 along the line CC, may, for example, be any one of the cross sections shown in FIGS. 2, 3, 4, 5 and 6.

FIG. 10 shows how the connector pin or pin element 74 shown in FIG. 9 may be employed to interconnect conductors on a pair of printed circuit boards '76 and 78 that are positioned in face-to-face abutment for the purpose of electrically connecting two circuit boards. Each of the two boards is provided with a bore 84) and a portion of a printed conductor 82 on each printed circuit is extended into the corresponding bore to form a conductive liner for the bore as indicated at 84 in FIG. 10. Thus each of the two conductive liners 84 constitutes a socket to receive the pin element 43.

if the pin element 43 is of the construction indicated in FIG. 2, the cross section along the line A-A of FIG. 10 will be as indicated in FIG. 14; if the pin element 43 is of the construction shown in FIG. 3, the cross section along the line A-A of FIG. 10 will be as indicated in FIG. 15; if the pin element 43 is of the construction shown in FIG. 4, the cross section along the line A-A of FIG. 10 will be as shown in FTG. 16; if the pin element 43 has the construction indicated in FIG. 5 the sections AA will be as indicated in FIG. 17; if the pin element 43 has the construction shown in MG. 6 section AA will be as indicated in FIG. 18; if the pin element 43 has the cross section indicated in FIG. 6 the cross section A-A will be as indicated in FIG. 18. The inner circumferential surface of a socket formed by a liner 84 has a radius which is equal to the radius of curvature of the outer surfaces of the helical wires of the pin element in the region where the pin element is expanded. In each instance the diameter of the socket is the diameter of the intermediate circle in each of the corresponding FIGS. 2, 3, 4, 5 and 6.

FIGS. 11 and 12 show how a pin element generally designated 85 may be fabricated by adding a second set of helical wires 87 which in turn are wound on a core wire 88 that is formed with helical indentations 89. The outer set of helical wires 86 is wound in the opposite direction from the inner set of helical wires 87 and the op- :posite ends of the outer helical wires are welded both to the opposite ends of the inner helical wires to the opposite ends of the axial core wire 88 to form the welded noses and 91. All of the helical wires of the two sets are biased radially outward from the core wire.

FIG. 13 shows how the pin element shown in FIG. 11 may be employed in the same manner as in FIG. 10. Thus in FIG. 13 two printed circuit boards 94 and 25 are positioned in face-to-face abutment, each board being provided with a bore 96 with a portion of a printed conductor 98 on each board extended into the corresponding bore in the form of a conductive liner 11M). This pin element being of the cross-sectional configuration shown in FIG. 12 fits into each of the two sockets or liners 100 in the manner shown in cross section in FIG. 19 where the inside diameter of the socket corresponds to the intermediate dotted circle in FIG. 12.

FIG. 23 shows how two pin elements 43 of the construction shown in FIG. 9 may be mounted in the opposite ends of a ferrule 192 to form a double ended pin connector. The opposite pin elements of the connector may be inserted in corresponding sockets. FIG. 24 is similar to FIG. 23 with the previously described thicker pin elements 84 (FIG. 11) mounted in a ferrule 104.

FIG. 25 shows how a pin element 195 such as the pin element 43 in FIG. 9 or the pin element 85 in FIG. 11 may be welded in end-to-end relationship to a soft metal shank member 166. The shank member 106 may be a piece of soft copper wire slightly smaller in diameter than the pin element. It is less expensive to provide a pin element with a soft copper shank member in this manner than to fit the pin element with a ferrule in the manner shown in FIG. 1. An advantage of this construction of a pin element is that the soft copper shank may be extended through an aperture in a bore in a printed circuit board and may be deformed into permanent engagement with the bore.

FIGS. 2631 show how the principles of the invention may be applied to the construction of a multiple conductor electrical connector. Such a connector may be employed, for example, to releasably interconnect two multiple wire cables or may be employed to releasably connect a multiple wire cable to a multiple circuit device.

FIGS. 26 and 27 show a multiple socket electrical connector, generally designated 110, in which a block 112 of dielectric material is mounted in and protrudes from a rectangular case 114. The case 114 has a nipple portion 115 to receive the end of a multiple wire cable 116 and inside the case the individual wires 118 of the cable are connected to corresponding metal tubes 120 that are fixedly mounted in the dielectric block 112 to serve as sockets to receive resiliently contractible pin elements.

A complementary multiple pin electrical connector is designated 122 in FIGS. 28 and 29 and comprises a metal case 124 with a block 125 of dielectric material mounted in the case and set back from the open end of the case. The case 124 is formed with a nipple portion 126 to receive the end of a second cable 128 and inside the case the individual wires 13ft of the second cable are connected respectively to corresponding pin elements 132 that are embedded in the block 125. The pin elements 132 may be similar in construction to the previously described pin elements 43 and 85 shown in FIGS. 9 and 11, respectively, but of longer length or, if desired, the pin elements may be of the construction shown in FIG. 25 with the shank members 106 of the pin elements embedded in-the block 125.

When the two electrical connectors 110 and 122 are mated in the manner shown in FIG. 30, the outer case 124 of the connector 122 telescopes over the block 112 of the electrical connector 110. The two electrical connectors 110 and 122 may be suitably indexed so that they can be assembled with only one orientation of the electrical connector 110 relative to the electrical connector 122. For example, the dielectric block 112 of the electrical connector 110 may be provided with an off-center groove 134 to receive a corresponding key in the form of an inner rib 135 of the case 124 of the electrical connector 122.

FIG. 31 shows how a pin element 132 of the electrical 9 connector 122 fits into a pin socket 120 of the electrical connector 110. The cross section E-E of FIG. 32 may be as shown in any one of FIGS. 14-19.

The invention meets a certain troublesome problem that arises from two facts. The first fact is that conventional pin connectors commonly deteriorate badly with respect to resistance to withdrawal from cooperating socket connectors and, especially so, when the electrical connections are made and broken repeatedly. Because of the fact effective withdrawal resistance after a period of use can be assured only by starting with a high initial resistance to withdrawal. The second fact is that it is difficult to manufacture pin connectors in large quantities to fall within a narrow range with respect to magnitude of resistance to withdrawal of the pin connectors from cooperating socket connectors.

Because of these facts, it has been necessary heretofore to accept an unduly high initial resistance to withdrawal and to accept a wide range of initial resistance. In too many instances the initial resistance afforded by a new pin connector is high in the liberal range. In practice, if a certain given minimum magnitude of resistance to withdrawal is required for a given installation, a much higher magnitude than the required minimum must be accepted. In many instances, such a wide range of withdrawal resistances creates difficulties. For example an umbilical cord for readying a missile for launching commonly incorporates a large number of releasable electrical connections provided with pin connectors and cooperating socket connectors and the total resistance to withdrawal of the large number of pin connectors may be seriously excessive.

The invention meets this problem by providing a pin connector that offers resistance to withdrawal within only a narrow range of tolerances and that may be depended upon to maintain substantially the same magnitude of resistance to withdrawal after repeated usage over a long service period. Thus the two connectors 110 and 122 with a large number of pin elements fitting into corresponding sockets may be easily manually separated in contrast to conventional connectors of the same general itype.

As heretofore stated, in the fabrication of a pin connector of this character outer wires are first wound helically tight around a core wire to make a strand of wires and then the strand of wires is drawn through a die orifice that contracts the strand with consequent forcing of the relatively soft copper core with resulting formation of indentations in the core. It has been found that this early step of drawing the strand of wires through an orifice may be employed for a further function of deforming the outer helical wires of the strand in a manner that results in greater surface contact of the pin element with a surrounding socket. Thus the early step of drawing a strand of wires through a reducing orifice may be carried out in such manner as to eliminate the need of subsequently employing the dies shown in FIGS. 7 and 8.

The first step in fabricating a reducing orifice die for the dual purpose is to form a bore 140 in a block 142 of suitable metal, for example a suitable grade of tool steel as shown in FIG. 32. The diameter of the bore 140 is the diameter of the socket in which a pin element is to fit and, of course, this diameter is larger than the outside diameter than the strand of wires because a pin element fabricated from a short length of the strand is subsequently expanded to a larger diameter than the initial diameter of the strand.

The next step in the fabrication of the orifice die is to remove a slice of theblock 142 as indicated by the two dotted lines 144. Finally, the two reduced halves 142a of the block 142 are firmly interconnected, for example by cap screws 145 as indicated in FIG. 33. The result is a die which forms a non-circular orifice 146, each of the reduced halves 142a of the die forming a corresponding sector 146a of the reduced orifice. The material that is removed by cutting the block 142 along the dotted line 144 is calculated to reduce the area of the final orifice 146 to an area that will result in crowding the wires of the strand together sufi'i-ciently not only to indent the core of the strand but also to deform the outer helical wires of the strand to form surfaces thereon of the same radius of curvature of the inner circumferential surface of the socket with which the pin fittings are to cooperate.

FIG. 34 shows, by Way of example, a strand of wires comprising a core wire 148 and six outer helical wires 150 each of which is of circular cross-sectional configuration. The cross-sectional area defined by the outside diameter of the strand shown in FIG. 34 is substantially larger than the diameter of the die orifice 146 along the dotted line 154. When the strand of the cross section shown in FIG. 34 :is forceably drawn through the die orifice 146, the wires of the strand are crowded together as shown in FIG. 35. Thus each of the outer wires 150 is deformed to provide an outer surface 150a of the wire that is of a radius of curvature equal to the radius of curvature of the socket in which a pin fitting is to be inserted.

It is to be noted that the die orifice 146 shown in FIG. 33 is of a cross-sectional configuration that is defined by a plurality of arcs each of which is of the same radius of curvature as the inner circumferential surface of the sockets in which the ultimately formed pin elements are to be inserted and that the cross-sectional area of the die orifice 146 is less than the area of a circle of the same radius of curvature. In this instance the plurality of arcs comprise two arcs but it is obvious that the cross-sectional configuration may he defined 'by any number of arcs. For example, the block shown in FIG. 32 obviously could be cut into four quarters by taking a slice out of the block at from the slice shown in dotted lines in FIG. 32. Thus when a strand of wires is crowded into the die orifice as shown in FIG. 35, the consequent minimum cross-.sec tional area of the strand may be described as conforming to a circumferential series of arcs of the radius of curvature of the contemplated sockets, the cross-sectional area of the compact strand being less than the cross-sectional area of a circle of the same radius as the arcs.

When the strand of wires passes from the die orifice 146, the outer wires spring loose slightly and when subsequently a pin fitting fabricated from a short length of the strand is expanded, either by an untwisting operation or an endwise impact operation, the cross-sectional configuration of the pin element expands to the configuration.

When the pin element is inserted into a socket having the inside diameter of the bore 146 in FIG. 32, the outer curved surfaces 150a of at least the two diametrically opposite wires 15Gb will match the inside curvature of the socket for extensive surface-to-surface contact therewith.

This second and alternate procedure for reforming the outer surfaces of the outer wires of a pin element does not provide the precise mating of all of the outer wires with thesurface of the surrounding socket but does result in increased area of contact between the pin element and the socket with consequent reduction of the unit pressure to the desired degree.

My description herein of the selected embodiments of the invention in specific detail will suggest various changes, substitutions and other departures from my disclosure within the spirit and scope of the following claims.

I claim:

1. Electrical connector means for interconnecting two conductors in a circuit, comprising:

a pin element for connection to one of the two conductors; and

a socket element for connection to the other of the two conductors,

said pin element comprising at least one wire defining a core and a cluster of resiliently flexible wires surrounding the core with one end of each wire of the It 1 cluster fixedly connected to the corresponding end of the core and with the other end of the wires of the cluster fused with the other end of the core and forming therewith a smooth rounded nose for a leading end of the pin element, the intermediate portions of the wires of the cluster being bowed resiliently outward from the core to give the intermediate portion of the pin element a given maximum outside diameter when the pin element is unrestrained, the intermediate portion of the pin element being contractible by constrictive force to a given minimum cross section at which the wires of the cluster are flexed inwardly into abutment with the core whereby the intermediate portion of the pin element exerts progressively increasing radially outward pressure in response to progressive contraction from said maximum outside diameter to said minimum cross section,

said socket element being of cylindrical configuration with a predetermined inside diameter intermediate said maximum and minimum diameters to cause the pin element to frictionally engage the socket element with radial pressure within a predetermined acceptable range of radial pressures to require a separation force for withdrawal of the pin element within a predetermined acceptable range of separation forces,

the intermediate portions of the wires of the cluster being noncircular in cross section with outer curved surfaces of a radius of curvature equal to the inside radius of the socket element for surface-to-surface contact with consequent reduced radial pressure-by the pin element against the inner wall of the socket element per unit area of contact between the two elements,

the cross-sectional configuration of said pin element when constricted to the minimum outside diameter being characterized by numerous indentation means permitting said core and said cluster of wires to be nested together with a wire in each of said indentation means for increased range of contraction of the pin element.

2. Electrical connector means as set forth in claim 1 in which said core comprises three wires twisted together and said cluster comprises at least one layer of helically formed wires.

3. Electrical connector means as set forth in claim 1 in which said core comprises three wires twisted together helically in one direction and said cluster comprises a layer of wires twisted helically in the opposite direction.

4. Electrical connector means as set forth in claim 1 in which said core comprises a single wire and said cluster of wires comprises two layers of oppositely wound helical wires.

5. Electrical connector means as set forth in claim 1 in which said numerous indentation means are on the core of the pin element and the wires of the cluster fit into the indentation means.

6. An electrical connector for interconnecting two pluralities of conductors, comprising:

a first connector having a corresponding plurality of socket elements for connection respectively to one of the two plurali-ties of conductors; and

a complementary second connector having a corresponding plurality of pin elements for connection respectively to the other of the two pluralitics of conductors,

each of said pin elements comprising a core and a cluster of resiliently flexible wires surrounding the core with one end of each wire of the cluster fixedly connected to one end of the core and the other ends of the wires of the cluster fused with the other end of the core and forming therewith a smooth rounded nose for a leading end of the pin element,

the intermeiate portions of the wires of the cluster of each pin element being bowed resiliently outwardly from the core to give the intermediate portion of the pin element a given maximum outside diameter when the pin element is unrestrained,

said intermediate portion of each pin element being contractible by constrictive force to a given minimum outside diameter in which the wires of the cluster are flexed inwardly into abutment with the core whereby the intermediate portion of the pin element exerts progressively increasingly radially outward pressure in response to progressive contraction from said maximum outside diameter to said minimum outside diameter,

the cross-sectional configuration of each of said pin elements when constricted to the minimum outside diameter being characterized by numerous indentation means permitting said core and said cluster of wires to be nested together with a Wire in each of said in dentation means for increased range of contraction of the pin element,

each of said socket elements being of cylindrical configuration of a predetermined inside radius and a diameter intermediate said maximum and minimum diameters to cause each pin element to frictionally engage the corresponding socket element with radial pressure to require a separation force for withdrawal of a pin element from the socket element,

the intermediate portions of the wires of the cluster at the outer periphery of each of the pin elements being of noncircular cross-sectional configuration with outer curved surfaces of the same radius as said inside radius of the socket elements for surface-to surface contact of each pin element with the corresponding socket element as distinguished from the line contact with consequent reduced radial pressure by the pin element against the inner wall of the socket element per unit area of contact between the two elements,

said predetermined inside diameter being selected to require a separation force within a given range of magnitudes to require a total separation force within a given range of magnitudes for separation of the first and second connectors,

said range of total separation force having an upper limit acceptable for convenient manual separation of the two connectors.

7. Means electrically interconnecting two contiguous components, comprising:

two socket elements of a given uniform inside diameter mounted in coaxial alignment in the two components respectively; and

a single pin element having its opposite ends telescoped into the two socket elements,

said pin element comprising a metal core and a cluster of wires surrounding the core,

the opposite ends of the core being fused to the corresponding ends of the Wires of the cluster and forming therewith two opposite smooth noses to facilitate entry of the opposite ends of the pin element into the two socket elements,

intermediate portions of the wires of the cluster being bowed outward from the core to give the intermediate portion of the pin element a given maximum outside diameter when the pin element is unrestrained by the two socket elements,

said intermediate portion of the pin element being contractable by constrictive force to given minimum outside diameter at which the wires of the cluster are flexed inwardly into abutment with the core whereby the intermediate portion of the pin element exerts progressively increasing radially outward pressure in response to progressive contraction from said maximum outside diameter to said minimum outside diameter,

said given inside diameter of the two socket elements being intermediate said maximum and minimum diameters,

the intermediate portions of the wires of the cluster being noncircular in cross section with outer curved surfaces of a radius of curvature equal to the inside radius of the socket elements for surface-to-surface contact with consequent reduced radial pressure by the pin element against the inner walls of the two socket elements per unit area of contact between the pin element and the socket elements,

the cross-sectional configuration of said pin element when constricted to the minimum outside diameter being characterized by numerous indentation means permitting said core and said cluster of wires to be nested together with a wire in each of said indentation means for increased range of contraction of the pin element.

8. The combination of:

an axial core of at least one wire;

a cluster of resiliently flexible wires surrounding the core,

the opposite ends of the wires of the cluster being welded to the corresponding ends of the core and thus forming solid noses,

the intermediate portions of the wires of the cluster being bowed radially outward from the core to permit resilient radial contraction of the cluster,

said core and cluster forming a pin element having a given maximum diameter in its unrestrained state and being capable of radial contraction to a minimum cross-sectional area at which the cluster wires abut the core;

a socket element for electrically connecting the pin element to a, conductor, said socket element being telescoped over one of the two ends of the pin element and being of a cross section intermediate the maximum and minimum cross sections of the pin element to resiliently contract a portion of the pin element to create pressure contact between the pin element and the inner surface of the socket element; and

a second socket element for electrically connecting the pin element to a second conductor, said second socket element being of the same cross-section as the first socket element and being telescoped over the other of the two ends of the pin element to resiliently contract a portion of the pin element to create pressure contact between the pin element and the inner surface of the second socket element,

the outwardly bowed portions of the wires of said cluster at the periphery of the pin element being noncircular in cross section and being formed with curved outer surfaces of a radius of curvature equal to the radius of curvature of the inner surfaces of the two socket elements,

the cross sectional configuration of said pin element when constricted to the minimum cross-sectional area being characterized by numerous indentation means permitting said core and said cluster of wires to be nested together with a wire in each of said indentation means for increased range of contraction of the pin element.

References Cited by the Examiner UNITED STATES PATENTS 2,683,207 7/1954 Lewis et al. 3,028,573 4/1962 Stoehr 339--18 X 3,031,641 4/1962 Camzi. 3,056,940 10/1962 Winestock 33964 3,255,430 6/1966 Phillips 339252 FOREIGN PATENTS 527,883 6/1955 Italy.

217,599 2/ 1942 Switzerland.

226,546 7/ 1943 Switzerland.

MARVIN A. CHAMPION, Primary Examiner.

P. TEITELBAUM, Assistant Examiner. 

1. ELECTRICAL CONNECTOR MEANS FOR INTERCONNECTING TWO CONDUCTORS IN A CIRCUIT, COMPRISING: A PIN ELEMENT FOR CONNECTION TO ONE OF THE TWO CONDUCTORS; AND A SOCKET ELEMENT FOR CONNECTION TO THE OTHER OF THE TWO CONDUCTORS, SAID PIN ELEMENT COMPRISING AT LEAST ONE WIRE DEFINING A CORE AND A CLUSTER OF RESILIENTLY FLEXIBLE WIRES SURROUNDING THE CORE WITH ONE END OF EACH WIRE OF THE CLUSTER FIXEDLY CONNECTED TO THE CORRESPONDING END OF THE CORE AND WITH THE OTHER END OF THE WIRES OF THE CLUSTER FUSED WITH THE OTHER END OF THE CORE AND FORMING THEREWITH A SMOOTH ROUNDED NOSE FOR A LEADING END OF THE PIN ELEMENT, THE INTERMEDIATE PORTIONS OF THE WIRES OF THE CLUSTER BEING BOWED RESILIENTLY OUTWARD FROM THE CORE TO GIVE THE INTERMEDIATE PORTION OF THE PIN ELEMENT A GIVEN MAXIMUM OUTSIDE DIAMETER WHEN THE PIN ELEMENT IS UNRESTRAINED, THE INTERMEDIATE PORTION OF THE PIN ELEMENT BEING CONTRACTIBLE BY CONSTRICTIVE FORCE TO A GIVEN MINIMUM CROSS SECTION AT WHICH THE WIRES OF THE CLUSTER ARE FLEXED INWARDLY INTO ABUTMENT WITH THE CORE WHEREBY THE INTERMEDIATE PORTION OF THE PIN ELEMENT EXERTS PROGRESSIVELY INCREASING RADIALLY OUTWARD PRESSURE IN RESPONSE TO PROGRESSIVE CONTRACTION FROM SAID MAXIMUM OUTSIDE DIAMETER TO SAID MINIMUM CROSS SECTION, SAID SOCKET ELEMENT BEING OF CYLINDRICAL CONFIGURATION WITH A PREDETERMINED INSIDE DIAMETER INTERMEDIATE SAID MAXIMUM AND MINIMUM DIAMETERS TO CAUSE THE PIN ELEMENT TO FRICTIONALLY ENGAGE THE SOCKET ELEMENT WITH RADIAL PRESSURE WITHIN A PREDETERMINED ACCEPTABLE RANGE OF RADIAL PRESSURES TO REQUIRE A SEPARATION FORCE FOR WITHDRAWAL OF THE PIN ELEMENT WITHIN A PREDETERMINED ACCEPTABLE RANGE OF SEPARATION FORCES, THE INTERMEDIATE PORTIONS OF THE WIRES OF THE CLUSTER BEING NONCIRCULAR IN CROSS SECTION WITH OUTER CURVED SURFACES OF A RADIUS OF CURVATURE EQUAL TO THE INSIDE RADIUS OF THE SOCKET ELEMENT FOR SURFACE-TO-SURFACE CONTACT WITH CONSEQUENT REDUCED RADIAL PRESSURE BY THE PIN ELEMENT AGAINST THE INNER WALL OF THE SOCKET ELEMENT PER UNIT AREA OF CONTACT BETWEEN THE TWO ELEMENTS, THE CROSS-SECTIONAL CONFIGURATION OF SAID PIN ELEMENT WHEN CONSTRICTED TO THE MINIMUM OUTSIDE DIAMETER BEING CHARACTERIZED BY NUMEROUS INDENTATION MEANS PERMITTING SAID CORE AND SAID CLUSTER OF WIRES TO BE NESTED TOGETHER WITH A WIRE IN EACH OF SAID INDENTATION MEANS FOR INCREASED RANGE OF CONTRACTION OF THE PIN ELEMENT. 